With legalization of marijuana expanding and the risk of marijuana-associated impaired driving increasing, a handheld device—much like a breathalyzer for alcohol—is urgently needed to rapidly quantify levels of cannabinoid compounds, such as tetrahydrocannabinol (THC) of suspected users at the roadside. Published data [1-3], all of which are hereby incorporated by reference in their entireties with respect to the use of THC in breath as a superior indicator of recent marijuana usage as compared with traces of THC in blood or urine, suggest that THC in breath is a better indicator of recent marijuana use and impairment compared to THC in blood or urine due to their long clearance times [4-7], all of which are also hereby incorporated by reference in their entireties with respect to the use of THC in breath as a superior indicator of recent marijuana usage as compared with traces of THC in blood or urine. Testing for THC in breath at the roadside would be convenient, non-invasive, and leverages the wide acceptance of administering a breath test at the roadside, as is commonly employed for alcohol.